Portable refrigerator



FIG. 1 is a perspective view of a portable refrigerator showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof;

FIG. 7 is a bottom view thereof; and,

FIG. 8 is a perspective view thereof, showing the handle in retracted position.

The broken lines depict portions of the portable refrigerator that form no part of the claimed design. 

CLAIM The ornamental design for a portable refrigerator, as shown and described. 